Process for producing brass powder



July 14, 1953 J. E. DRAPEAU, JR., ETAL 2,645,573

PROCESS FOR PRODUCING BRASS POWDER Filed July 24, 1946 SUPPL Y/Qfoz/cr/av ro @9,455 pon/p5@ f/z, C0, cm, @as

af Mod-M507 amano/,en

K -zna c-| A/R SEPT/QA T10/v l Josep/7 E. rapeaa, Jr.

Naf/1an 5. arbef; J/ CL EAN @RASS Pawof/e 1 INVENTORS Afr? PROCESS FORPRODUCING BRASSVPOWDER Joseph E. Drapeau, Jr., Calumet City, and NathanB. Barber, Jr., Chicago, Ill.; said Drapeau, Jr., assignor to TheGlidden Company, Cleveland,

Ohio, a corporation of Ohio Application July 24, 1946, serial NoI685,794

|Iehis invention relates to a process for producing brass powderrbyreducing zinc oxide with gaseous reducing agents at elevatedtemperatures in the presence of metallic copper, and also relates to anextended process of like character by means of which brass-containingmaterial, and mixtures of brass with zinc, zinc oxide and/or copper maybe convertedrto brass powder.

We have found `that while zinc oxide cannot pounds of copper, such ascopper oxides, hydroxl ides, carbonates orbasio carbonates. By reason ofthis latter discovery, we are able to employ a leaching process as ameans for obtaining a mixture of zinc oxide and copper oxide which canbe made suitable for reduction into brass powder. Moreover, since such aleaching process is suitable, we are able to use scraprbrass, zinc andcopper as raw materials from which the copper and vzinc components ofthe brass vpowder are derived. Accordingly, by means of this inventionit becomes possible to treat secondary orscrap brass by an economicaland eiicient process to convert the same into a relatively valuablebrass powder which is eminently suited. for fabrication 2 claims. (o1.75-5) Figure 1 is a diagrammatic representation of a muie furnacesuitable for use in effecting thereduction of mixed oxidic zinc andvcopper, 'compounds to produce brass powder.

Figure 2 is allow sheet indicating one type of metallurgical process bywhich copper and zinc, or brass may .be converted into brass powder.

This invention isbasedin part on our discovery that zinc oxidecan'be-reduced by means of gaseous reducing agents at relatively lowtemperatures if metallic copper in nely-divided form is intimatelydispersed throughout the zinc oxide.` We have found that the reductiontemperatures are high `enough to permit the reduced zinc to be absorbedrapidly by the copper to form brassparticles, yet are low enough toavoid appreciable losses of'zinc by vaporization. The reduction alsoavoids any appreciable agglomeration of the brass powder into coarselumps or masses, with the result that the brass particles are recoveredin finely-divided form, and a simple milling operation is all Athat isrequired to convert them into soft, easily-compressible pown l 1.1i

into 'a variety of machine parts or elements by well-known powdermetallurgical processes;

i Accordingly, it is an object of this invention to convert brass orscrap brass into brass powder.

Itis another object of the invention to produce brass powder by athermal reduction of zinc oxide in the presence of metallic copper.

It is a further object to treat prime or secondary copper, zinc andbrass by hydro-metallurgical means to produce a mixture of oxidic zincand copper compounds which can be treated by thermalreduction methods toproduce brass powder.

These and other objects will be apparent from the `followingdescription, taken` in Vconjunction with the accompanying drawings-in'whichz ders of-desired neness. Y

The invention is based-in'further part on our i discovery that when amixture of oxidic zinc compounds with oxidic copper compoundsissubjected to reduction by means of hydrogen, carbon monoxide or theirmixtures, the copper" compounds can be reduced practically completelybefore any' appreciable reduction of zinc oxide begins. Accordingly, thereduction of such a mixture naturally occurs-in such sequence thatiinely divided porous metallic copper is provided in the charge bythe'time-it's-presence is needed to promote the reduction ofthe zincoxide. Itwill be understood, of course, thatv a co-reduction of amixture of Zinc oxide `and oxidiccfopper compounds' is not required,since the production of brass'powder in accordance with the inventioncan lbe achieved equally -well by mixing metallic copperv powder withzinc oxide or oxidic zinc compounds and subjecting this mixturel toreduction. Nevertheless, a co-reduction of the mixed oxidic compounds isadvantageous in that it peri y mits oneAto produce the finely dividedcopper in situv in a porous condition, and to employ metallic brass asthe raw material from which the zinc and copper constituents ofthedesired brass powder may be obtained, That is, we have found thatmetallic brass can be subjected to a leaching treatment with ammoniumcarbonate solutions whereby the zinc and copper of the brass may bedissolved. The resulting solution may then be treated in a simple mannerto precipitate the zinc and copper thereof in the form of oxidic zincand copper compounds. This oxidic precipitate may then be dried, itscomposition adjusted to produce a brass powder of desired composition,finely ground, and then subjected to thermal reduction to produce thedesired brass powder. By employing such a process, and by usingsecondary or scrap brass as the'raw material, a relatively cheap rawmaterial may be converted economically into a brass powder ofconsiderable value and marketability. It will berec'ognized, however,that the invention may be practised in its broadest aspects withoutemploying such a leaching process, since zinc oxide and oxi'dlc zinccompounds from any source may be mixed with either copper powder oroxidic copper compounds from any suitable sources, and the (mixturereduced thermally in accordance with the invention to produce brasspowder. Nevertheless, there are obviousv economic advantages in aprocess which employs secondary brass lrather than prime zinc oxide andcopper oxide as the raw material. e

The foregoing aspects of the invention may now be more fully explainedin connection with specie examples which illustrate, but do not limit,the various features of the invention.

REDCTION EcmpleI Different batches of the mixture were then sub-r jectedto reduction in ajmufe furnace of the type illustrateddiagrammaticallyiin Figure 1.

The furnace consisted of athermally insulated electric resistanceheating unit yI surounding an elongated muiile tube r2 about` one inchin diameter composed of vsilica or chrome-.nickel steel. The muie wasclosed at one end by Va lcap `3 and partially closed at the other end bya rcap-ll having an exhaust port in it. Hydrogen could be admitted tothe muflie through inlet 6 provided with valve 1, while nitrogen couldbe admitted through inlet provided with valve 9. Temperaturemeasurements were made by means of thermocouple l secured in the wall ofthe muiiietube in the hottest portion thereof. In eachcasethe batch ofmixture to be reduced was spread out in a tray to form a uniform layerof the thickness indicated in the following table. The procedure ofhandling each tray then consistedv in flushing the mufle out Withhydrogen while adjusting the electric input of the heating unittoestablish the desired temperatureas measured bythe thermocouple. Theflow of hydrogen was stabilized at about 6 cubic feet per minutemeasured at Iroom temperature after which the tray was put into themuiile at position A and allowed to remain there a few minutes. It wasthen pushed as by rod lil into the hot zoneeof the mule, as at positionB, and allowed toY remain inv that position for the time indicated inthe table. It was then pushed to position C where it was allowed tocool. After' Thevproportions were such as to the tray and its contentshad cooled to about room temperature, valve 'I was closed and valve 9was opened, thus allowing nitrogen to enter the muie, and to flush outthe hydrogen. Cap 3 was then removed, and the tray with its layer ofcharge was taken from the muie and examined. Meanwhile another tray hadbeen inserted in the muie at position A.

cent Zn cent Cu V 23. 18 76. 82 Traces of alloying. l/ 28. 16 71.84Incomplete Alloying. I 25. 04 74. 96 Complete Alloying. y; 26. 77 73. 33M 25. 86 74. 14

M 21. 77 78. 23 Zinc Distillation. 12. 83 87. 17 D0.

The tests of Example I and other tests of like nature' have shown thatthe reduction temperature isrrather critical, in that too low atemperature Yfails -fto effectA complete alloying and reduction of thezinc oxide while 'too high'atemperature produces undesirable flesses ofzincbydistilla'tion. VlTempera-turesbetween 'about 14'00" F. and'1550oF. provide reduction-rates and recoveries which appearto be commerciallydesirable. The tests also indicate that the thickness of the layer whichis being reduced is a factor since thick layer-s require VVa longerreduction time Layers aboutilfthicklare preferred because-'with suchthicknesslthe reduction'can be completed Aat lower tempera-turesin'shor'ter times, and with good recoveries. Thinner layers lmay be usedalso,of course. The tests indicate thatthe rate ofreduction isaiunctionalso ofthe rate ofgflow of "hydrogen r"We have found thatratesof ybetween about AZand 20 cubicfeet per minute measured at roomtemperature are effective without being wastfulfalthoug'rh rates'betweenabout 2 and"10fcubicfeet perminutevare 'preferred for ecnomicirea-s'ens.It will loe-recognized by those skilled in thelartthatthe factorsof'rate of flow, temperature, time, and layer thickness are allinterdependent, A'and that therefore'many combinaticnsl'oithese'factorsf can'be employed within the limits set outv generally'above, to accomplish the ipurposes of `the invention.

vIn similar reduction tests where larger propotion'sef zinc oxide wereused, it was found that brass powders cotaining'morefthan about 30%zinc-c0uld not beproduced.

- e Y ExampleII In'aseries` of tests made under conditions simiylar tothose'of Example VLa part ofthe ne zinc cxidefwas intimatelymixed-with'all of the copper oxide. The balance of the fine zinc oxidewas spread evenly-over the bottom of the tray and was then lcovered withthe copper loxide-zinc oxide mixture. The' ratio of total coppertototalzinc in-eachtray was maintained'at 70:30, but

'the ratio of copper -tozin'ciin the top layer of each tray was'less,vthe ratios varying from\70:30 to :1. It was found that soft'brasspowders could-beobtained in this rway 'and that the recovery ofAzinc'was increased' somewhat,especial1y where the bulk of the totalzinc oxide `was in the bottomlayer. Y

-k-In similar vtests where no zinc oxide was incorporatedin the toplayer it was found that the copper oxide was reduced irst and that thezinc distilled up into the copper layer and formed a hard brass layerthat could not be milled into powder. These tests indicate that when`the zinc oxide is mixed with the copperV oxide, it aids in keeping theindividual particles of reduced metal from sintering or otherwiseagglomerating together to form coarse hard lumps'. `The presence of zincoxide in the copper. oxide thereby y makes it possible to obtain thereduced metal in the form of finely divided brass powder. :For thispurpose it may be desirable to leave a small amount of unreduced zincoxide inthe charge, and if necessary, to remove the unreduced residuefrom the brass powder after the latter has been removed from thefurnace. Such a separation of zinc oxide from the brass powder can bemade conveniently in air classifying apparatus of con- Ventional design.

While the foregoing examples have been explained in connection with theproduction of high-zinc brass powder, it will be recognized thatlow-zinc brass powder may be made equally well by adjusting the ratio ofcopper to zinc to produce the desired brass composition.

We have found, however, that it is diflicult to produce brass powderscontaining much less than 10% zinc if complete reduction of the zincoxide is effected, because at the temperatures involved in the practiseof this invention, the particles of low-zinc brass tend t0 agglomerateinto coarse lumps which are dicult to mill into powder. However, if thereduction is controlled so that a part of the zinc oxide remainsunreduced, this harmful agglomeration of the brass particles can beminimized, and brass powders containing upwards of about 4% of zinc canbe produced. The unreduced zinc oxide can be removed from the finishedpowder by conventional air separation methods as already noted above.

As indicated previously other gaseous reducing agents besides hydrogencan be used to effect the reduction of the copper and zinc oxides tomake brass powder. Carbon monoxide is very suitable. as are mixtures ofcarbon monoxide with hydrogen in all proportions. Methanol is also an`effective reducing agent since it decomposes at elevated temperaturesinto carbon monoxide and hydrogen. City gas containing more than about25% hydrogen and practically free of carbon dioxide, is also effective.Hydrocarbon vapors, such as those of methane, propane or butane are nottoo satisfactory because of their tendency to crack at elevatedtemperatures with the formation of free carbon. However small tosubstantial amounts of these latter vapors in city gas, for ex-Reactions 1 and 3 are easily reversible at elevated temperatures whereas2 and 4 occur predominantly toward the right. It is this differencewhich is primarily responsible for the early reduction of copper oxide,followed latter by the reduction of v zinc oxide, since the reduction ofcopper Voxide will continue rapidly toward the right even in thevpresence of considerable concentrations of'water 6 vapor and/or carbondioxide@ Onthe contrary', only small concentrations of these'productscanreversereactions land 3 so asto reoxidize any zinc that may be present.As a result therzinc oxide remains unreduced practically until watervapor and carbon dioxide are no longer generat- 'ed byreactions 2 and 4.At that time, if the flow of gaseous reducing agent is sufficientlyrapid, re-

actions 1 and 3 begin to occur' inthe forward direction, and continue aslong fas theflowoffthe reducing agent isl rapid enough to sweep thewavter vapor or carbon dioxidefaway as it is generated. If the rate offlow is tooslow to accomplish this, so that harmful concentrations'of-water vapor or carbon dioxide are permitted todevelop in theatmosphere around the charge then such concentrations may reach thepoint where reactions -1 and 3 occur at a greater rate in the reversedirection than in the forward direction, and reoxidation occurs. i Y

It will be recognized that the equilibria `of reactions l and 3 arealtered appreciably by the presence. of metallic copper.V in thelayersat the time that the zinc oxide is being reduced, since thereduced zinc alloys with the copper and is thereby removed, in a sense,from the zone of reaction, whereby the eifects 0f mass action favor theoccurrence of reactions l and 3 in their forward directions.

It will be appreciated from what has been said above that water vaporand carbon dioxide are harmful ingredients in the gaseous reducingagent, and should be kept at low concentrations in the agent when thelatter is introduced into the muie. Preferably the agents should bedried before being admitted to the furnace, and treated with ab- Ysorbents or by other known means to remove carcharge through theAfurnace 'should preferably be counter-current withrespect to the flow ofthe gaseous, reducing agent in order to minimize reoxidation reactions.When a continuous reduction of a mixture of oxidic zinc and coppercoinpounds is desired with counter-current move ment, as by conveyingthe charge through the furnace cna ,belt moving in a 'direction oppositeto the flow of the reducing agent, provision should be made for thepreliminary calcination of such compounds as the hydroxides, carbonates,and basic carbonates of zinc and copper, t0 ensure that the water vaporand/or carbon dioxide of these compounds is liberated well in advance ofthe zone in which the reduction of zinc oxide occurs, since otherwisethe products of calcination would promote re-oxidation of the zinc.These oxidic compounds are converted at relatively low temperatures(below about 350 C.) into the corresponding oxides, so that thecalcination would normally be completed long before the reductiontemperature of zinc oxide would be reached.

The brass powders made in accordance with this invention are easilymilled to the desired mesh sizes after they are removed from thereduction furnace. As a consequence the sized powders are retained in asoft, unwork-hardened condition, and may be briquetted with therelatively-low pressures of 10 to 30 tonsper square inch to producecompacts or briquettes which show good vgreen strength. n The compactsmay be sintered at temperatures around 1450213., preferably in a dryhydrogen atmosphere, and. for about 15 minutes, to produce dense bodies.Y'I'hc .sintered bodies have been found to exhibit considerably r`less'v shrinkage during sintering than comparable brass powder briquettesproduced 'from Apow-der maderby atomization of lmolten -found thatrifmetallic copper is present with 'the metallic zinc, or'that if oneattempts to dissolve zinc'out of brass, some copper is dissolved also,

particularly if the solution is aerated while the leaching is going on.It appears that an ammonium carbonateV solution, without aeration, willdissolve metallic zinc rapidly -and in volume,

but will dissolve metallic copper only very slowly.

If the solution is aerated, however, its effectiven'ess as a lixiviantfor both metallic zinc and cop- 19 Vingsindicatesthe-rtype vof processwhich is in- :'VGlVBd, andiindi'catespne preferred arrangement.firrifivhichfrecycling ofI intermediate products is employed yto attainlan femcient process.

The;leachingzprocess may be understood more rtuliytitromfthe ffoll'owing"examples of Table Il, Y.ii/#herein ."Zinc, copper, brass, and mixtures`oi metallic .zinc Vwith metallic-copper were treated with ammonium,carbonate solutions with and Without' aeration, 'and' solutions analyzedtol determine how much of each offthe metals had been dissolved. Allrtheresults'have been determined Nat -approximately-room-temperatureconditions.

TABLE Il (NHMCOE Bmw Solution Analysis Example N0 Concentra `tio'n .olfAgitation Aeration hy i im 19a@ 2me/m Cue/1.)

g,/l, Hrs. l. 80 20 No.. Woef. 60 2. 100 3 Yes. No 2.5 3. 100y Vi9 Yes(3 hrs.). Yes (16 his). 97.8 -80 116. -Yes(lirs.). No 32.9 5- S0 16 vYoYes(6hrs.) 54.9 6. so '16 Yes (6hrs.) No 43.0 o f 7. so Vis .No. 37.027.

8 so v 16 Yes (es-hr 11.3 10.6 9. so 16 o 15.8 29.9

per is improved. In the case of metallic copper, this improvementappears to result from the oxidation eiects of aeration on any coppersalts which are in solution, rather than from any appreciable effects onthe ammonium carbonate. Apparently some small amount of copper isdissolved at first by the carbonate solution, and aerarate metals inthat an ammonium carbonate solution Without aeration will dissolve both.Zinc and copper concurrently Ifrom brass. The action, however, isaccelerated by aerationfand is en- "hanced more in respect to copperthan-in respect to zinc. U

On the basis lcf these discoveries we have found it possible to leachbrass, metallic Zinc, metallic copper, or mixtures of metallic zincand', metallic copper, with ammonium. carbonate *solutiona preferablywith aeration, thereby to obtain car-l bonate solutions of either orboth oi' the metals. The metal values of the carbonate solutions cansubsequently be recovered principallyin the form of basic carbonates bya simple evaporation or distillation process'in which ammonia and partofthe carbon dioxide and water of the solutions is driven oi byboilingfthe solution at normal or reduced pressures. By such va.distillation.' the basic carbonates are precipitated;fromfthe:liquid andcan be ltered oi. Preferably-they-are then dried and calcined to convertthem Vto the corre-- 'From Example itwill be appreciated that whenbrass, preferably in such comminuted form 'asbrassturnings or borings,is leached with an ammonium carbonate solution under the condi-k tionsindicated, the .resulting ysolution contains copper and Zinc in theratio of about 1.5 to l.. Ii aeration is provided, however, as in.Example 9 the'ratio oi copper to zinc can be raised to approximately1.9 to l; that is, 'to approximately thera'tio or copper to Zinc'in the65:35 brass. `I'f eithersolution were to be treated in themannferexplained above to precipitateY the metals as afmixture of 'basiccarbonates, and the mixed carbonates were then to bereduced in the man-.ne'r also explained previously to produce, say '75:25` brass powder,'then copper in some form would have to be added to the mixture in orderto brin'gthe'ratioof Vcopperto Vzinc up to slightly less than Sto l'tocompensate for small vaporization losses Vo zinc. 'The additional coppercould be introduced in the lform of copper powder which could be mixedwith'the basic .carbonates beiore'or'after vthe 'latter had beencalcined. Or the copper necessary to raise the ratio could be obtainedin solution by "a leaching step oi the type shown by Example '3 .1 Such`a solution could be blended with the `solutions obtained by Examples 8or 9 in propcrtions necessary to v establish the propercopper-to-zincratio, or the copper content of the solution of Example 3-could befprecipitated, and the precipitate blended in suitableprnport'ons with the precipitate obtainedflfrom-Examples 80119. lOfcourse, copper )oxide could also be blended with the latter pre-`c'ipii'atesAforthe same pupose. In lilrernanner, ifY conditions arose'which required` the addition of lzinfc'to thereduction chargasuchZinccould be obtained by`treatments illustrated by Examples 1, 4, and 6,or could be introduced to the charge in the form of Zinc En. sun.- mary,therefore, it will 'ce recognized that th ,rds dtilde copper powder.

'I'he leaching process may be applied to different metallic andnon-metallic materials to recover their copper and/or zinc contents forconversion to brass powder. Brass of almost any zinc content may be usedalone or in combination with zinc or cooper or any of the follow.- ingmaterials. Leaded brasses are suitable since the ammonium carbonatesolutions do not eX- tract the lead, tin or iron contents of brasses.For the same reason bronzes and cooper-lead aggregates may be treated torecover their copper. Likewise copperplated iron may be treated forcopper, and copper-plated Zinc electrotype plates may be processed torecover either the copper or the zinc or both. However, in treatingmaterials containing lead, tin or iron, some of these metals appear inthe leach liquor in a colloidal condition, and should be removed fromthe latter before the copper and zinc basic carbonates are precipitatedin the evaporation or distillation step, supra. Copper or brasscontaining cobalt, nickel or silver should be avoided. unless theselatter metals can be tolerated in the brass powder, since they are alldissolved to some extent by the ammonium carbonate solutions. Crudenonmetallic materials such as zinc fume, or blue powder may be used. Itis apparent, of course, that the use of scrap or secondary materials ofthe kinds mentioned is preferred for economic reasons, but the practiseof the invention is not limited to their use.

A wide range of concentrations of ammonium carbonate may be used,depending on the economics of the process, but for most purposes aconcentration of between about 40 to 80 grams per liter is preferred.Concentrations higher than about 80 grams per liter can dissolve so muchcopper that they may become saturated in copper-ammonium-complex salts,and may produce troublesome crystallizations of these salts which clogup the equipment, coat the metal which is being leached, and otherwiseimpede the leaching process. Concentrations less than about 40 grams perliter may be economically undesirable because of the slower rates ofdissolution. A concentration of about 60 grams per liter is preferredbecause it appears to provide a satisfactory compromise between thesetechnological and economic limitations for commercial practise of theinvention.

Many modifications of the invention as herein described are within theability of those skilled in the art, and such modifications as comewithin the scope of the claims are contemplated as part of theinvention. For example, while relatively thin layers of charge arepreferred in the reduction process for the reasons noted, it is possibleto reduce relatively thick beds of charge by employing a revolvingreduction, furnace, or a furnace in which the charge can be suitablyrabbled to bring unreduced portions of the charge into effective contactwith the reducing agent. Furthermore, while scrap brass and other scrapmetals containing copper and zinc are preferred raw materials for theleaching process, numerous other secondary materials besides thosementioned previously are available and may be used with or withoutprevious beneficiation as a source of Zinc and/or copper recoverable byleaching with ammonium carbonate solutions. Various other details of theinvention are likewise subject to modication in accordance withabilities ci one skilled in the art, when guided by the foregoingdisclosure of the concepts and practise of the invention.

The foregoing leaching processes are described and claimed in ourcopencling divisional application Serial rio. SCI-"2,534, led August 15,1952.

'Having described the invention what is claimed 1s:

1. The method of producing soft, alloyed brass powder which is composedessentially of between about 4% and 30% of zinc, balance copper, andwhich is particularly adapted for use in making briquetted bodies havinggood green strength and good sintering properties, said processcomprising the steps of: subjecting to reduction at temperatures betweenabout 1400" and i550o iii. and in a flowing stream of gaseous reducingagenta loose, unconsolidiated, shallow layer consisting essentially ofan intimate 1 ure of aine oxide having a particle size below about lemicrons and at least one nely-divided cupriferous material selected fromthe group consisting or' metallic copper and oxidic copper compounds,the zinc oxide and cupriferous materials being proportioned in saidlayer to provide (a) zinc and copper contents therein in about theproportions required in the desired brass powder, and (b) to provide anexcess of zinc oxide thereover in an amount as hereinafter specified;continuing the reduction until any oXioLic copper compounds have beenreduced to metallic copper and until the major part of the Zinc oxidehas been reduced, but discontinuing the reduction while sufficientunreduced zinc oxide remains in the layer to effectively maintain theentire mass thereof in a powdery, substantially unsintered condition;cooling the layer under nonoxidizlng conditions and thereafterseparating the unreduced zinc oxide and recovering brass powder fromsaid cooled mass.

2. rhe process as claimed in claim l wherein the shallow layer has athickness of about 1/11l inch, and wherein said gaseous reducing agentis hydrogen.

JOSEPH E. DRAPEAU, JR. NATI-IAN B. BARBER, JR.

References Cited in the file of this patent UNTED STATES PATENTS NumberName Date 827,717 Edison Aug. 7, 1906 1,741,953 Ramage Dec. 31, 19291,829,635 Davey Oct. 27, 1931 1,875,722 Gabriel et al. Sept. 6, 19321,908,696 Dodge May 16, 1933 2,133,761 Tietig Oct. 18, 1938 2,254,976Powell Sept. 2, 1941

1. THE METHOD OF PRODUCING SOFT, ALLOYED BRASS POWDER WHICH IS COMPOSEDESSENTIALLY OF BETWEEN ABOUT 4% AND 30% OF ZINC, BALANCE COPPER, ANDWHICH IS PARTICULARLY ADAPTED FOR USE IN MAKING BRIQUETTED BODIES HAVINGGOOD GREEN STRENGTH AND GOOD SINTERING PROPERTIES, SAID PROCESSCOMPRISING THE STEPS OF: SUBJECTING TO REDUCTION AT TEMPERATURES BETWEENABOUT 1400* F. AND 1550* F. AND IN A FLOWING STREAM OF GASEOUS REDUCINGAGENT A LOOSE, UNCONSOLIDIATED, SHALLOW LAYER CONSISTING ESSENTIALLY OFAN INTIMATE MIXTURE OF ZINC OXIDE HAVING A PARTICLE SIZE BELOW ABOUT 10MICRONS AND AT LEAST ONE FINELY-DIVIDED CUPRIFEROUS MATERIAL SELECTEDFROM THE GROUP CONSISTING OF METALLIC COPPER AND OXIDIC COPPERCOMPOUNDS, THE ZINC OXIDE AND CUPRIFEROUS MATERIALS BEING PROPOTIONED INSAID LAYER TTO PROVIDE (A) ZINC AND COPPER CONTENTS THEREIN IN ABOUT THEPORPORTIONS REQUIRED IN THE DESIRED BRASS POWDER, AND (B) TO PROVIDE ANEXCESS OF ZINC OXIDE THEREOVER IN AN AMOUNT AS HEREINAFTER SPECIFIED;CONTINUING THE REDUCTION UNTIL ANY OXIDIC COPPER COMPOUNDS HAVE BEENREDUCED TO METALLIC COPPER AND UNTIL THE MAJOR PART OF THE ZINC OXIDEHAS BEEN REDUCED, BUT DISCONTINUING THE REDUCTION WHILE SUFFICIENTUNREDUCED ZINC OXIDE REMAINS IN THE LAYER TO EFFECTIVELY MAINTAIN THEENTIRE MASS THEREOF IN A POWDERY, SUBSTANTIALLY UNSINTERED CONDITION;COOLING THE LAYER UNDER NONOXIDIZING CONDITIONS, AND THEREAFTERSEPARATING THE UNREDUCED ZINC OXIDE AND RECOVERING BRASS POWDER FROMSAID COOLED MASS.